The field of this invention is pulp refining elements and the method of making same.
Pulp refining machinery utilizes rotating refining elements to condition pulp in preparation for the production of paper. The popular refining element types in use are either flat disk or conical in shape. The refining elements contain an array of closely spaced refining bars attached to a base, either disk or conical, and are used in pairs, either 2 flat disks or a male and female cone. The pulp is forced between the pair of elements where the refining bars perform the desired conditioning in well known fashion. Prior refining elements can further be classified generally as either manufactured or cast. Manufactured elements are those wherein the element is built up from individual refining bars and supporting members such as, for example, in U.S. Pat. No. 4,157,669. A cast element, on the other hand, is a one piece molding of essentially the entire element which may require some finish machine work such as, for example, in U. S. Pat. No. 3,815,834. Some elements are made in a hybrid manner as, for example, in U.S. Pat. No. 4,116,392 wherein a model of the disk is manufactured, a precision investment cast is made from the model, and the cast is then used to jig a set of manufactured bars for a cast base.
Both cast and manufactured prior elements have been expensive to make. Cast elements require less labor but are material intensive. Prior manufactured elements are highly labor intensive, such as for example in the '768 patent wherein each bar is individually jigged and hand welded into place. Further, the welding of prior manufactured elements produces excessive heat which can damage treatments performed on the refining bars for hardening. The welds of prior manufactured elements are also done on the refining side of the element where the roughness of the weld must either be machined smooth or covered with a filler to avoid interference with the refining process.